Imaging microstructural damage and plasticity in the hippocampus during epileptogenesis

Epileptogenesis refers to the development and extension of tissue capable of generating spontaneous seizures, resulting in the development of an epileptic condition and/or progression of epilepsy after the condition is established. The hippocampus is the seizure-initiating zone in many epilepsy patients as well as in animal models of epilepsy. During epileptogenesis, the hippocampus undergoes structural changes, including mossy fiber sprouting; alterations in dendritic branching, spine density, and shape; and neurogenesis. In vivo magnetic resonance imaging (MRI) techniques provide insights into the microstructural organization of the hippocampus. An assessment of the structural plasticity of the hippocampus may provide parameters that could be used as biomarkers for epileptogenesis. Here we review conventional and more advanced MRI methods for detecting hippocampal tissue changes related to epileptogenesis. In addition, we summarize how diffusion tensor imaging can reveal cellular damage and plasticity, even at the level of hippocampal subfields. Finally, we discuss challenges and future directions for using novel MRI techniques in the search of biomarkers associated with epileptogenesis after brain injury.